250 GEOGNOSY OF THE APPALACHIANS. [XIII. 



have the characters of the White Mountain series, appear, from 

 the incidental observations to be found in Lieber's reports, to 

 belong to a higher group than the chloritic and serpentine 

 series, and to dip at comparatively moderate angles.* 



Professor Emmons, whose attention was early turned to the 

 geology of western New England, did not distinguish between 

 the three types which we have defined, but, like Rogers in 

 Pennsylvania, included all the crystalline rocks of that region 

 in the primary system. It is to him, however, that we owe 

 the first correct notions of the geological nature and relations 

 of the Green Mountains. These, he has remarked, are often 

 made to include two ranges of hills belonging to different 

 geological series. The eastern range, including the Hoosic 

 Mountain in Massachusetts and Mount Mansfield in Vermont, 

 he referred to the primary ; which he described as including 

 gneiss, mica-schist, talcose slate, and hornblende, with beds and 

 veins of granite, limestone, serpentine, and trap. He declared, 

 moreover, that there is no clear line of demarcation among the 

 various schistose primary rocks, and cited, as an illustration, 

 the passage into each other of serpentine, steatite, and talcose 

 schist. His description of the . crystalline rocks of this range 

 will be recognized as comprehensive and truthful. 



[* My own observations have since shown me that the rocks of the White 

 Mountain series are largely displayed, and rarely at high angles, in the Blue 

 Ridge in Carroll County, Virginia, thence southwestward at least as far as 

 Ashe County, North Carolina, and again in Polk County, Tennessee. The 

 lithological study in these regions is rendered difficult by the fact that they 

 are covered, often to a depth of a hundred feet or more, by the undisturbed 

 products of their own decomposition, the protoxide bases having been re- 

 moved by solution from the feldspar and the hornblende, and the whole rock, 

 with the exception of the quartzose layers, reduced to a clayey mass, still, 

 however, showing the inclined planes of stratification. The immense veins 

 of pyritous copper-ores, which these rocks enclose (ante, page 217), have in 

 like manner been changed, to as great depths, into hydrous peroxide of iron. 

 I have already alluded to the significance, both chemical and geological, of 

 this decomposition, and to its great antiquity (ante, page 10). The observa- 

 tions of C. A. White, in the northwest, show that such a decomposition of 

 the Eozoic gneisses was anterior to the cretaceous period, while in Mi-Mum, 

 it appears from the studies of R. Pumpelly, confirmed by my own observa- 

 tions, that the quartziferous porphyries with which the iron-ores of that 

 region occur, were thus decomposed before the deposition of the Cambrian 

 sandstones.] 



